When various kinds of elements and devices such as a semiconductor element are manufactured, a composite substrate formed by joining two substrates to each other may be used in some cases. For example, when a semiconductor wafer level package is manufactured, a composite substrate formed by joining a semiconductor wafer and a support substrate to each other is used (Patent Literature 1). In this technology, in a semiconductor wafer or a support substrate forming the composite substrate, a cut line having a certain depth from a surface thereof is formed. Therefore, in a processing step after the cut line is formed, stress applied to the semiconductor wafer and/or a cap wafer is alleviated by the cut line. As a result, a warpage amount of the composite substrate is greatly reduced, and thus, in semiconductor processes after the cut line is formed, occurrence of various kinds of troubles such as an error in transporting the composite substrate, lowering of product yields, and the like can be inhibited.